There are currently many radio/wireless and cellular access technologies and standards such as Global System for Mobile Communications/General Packet Radio Service (GSM/GPRS), Wideband Code Division Multiple Access/High Speed Packet Access (WCDMA/HSPA), CDMA-based technologies, wireless fidelity (WiFi), Worldwide Interoperability for Microwave Access (WiMAX) and Long Term Evolution (LTE), to name but a few. Numerous technologies and standards have been developed during the last few decades, and it can be expected that similar developments will continue into the future. Specifications are developed in a variety of organizations such as the 3rd Generation Partnership Project (3GPP), 3GPP2 and IEEE.
Communication between network nodes such as base stations and user equipment may be based on standardization, standard protocols and standard specifications, allowing the parties to the communication to interact appropriately. There are some scenarios, however, where a UE or network node operates in ways that are not defined by standard. Some UEs, for example, have performance limitations that prevent them from implementing all of the features required by a standard. As an example, Category 0 devices may have certain performance limitations because they are equipped with only one receive antenna.
In some circumstances, it may be beneficial for a network node to enhance the coverage of essential downlink (DL) transmission messages if a UE is known to have such limitations. Accordingly, information regarding the coverage limitations should be known to the network node at an early stage of the UE entering the network. The UE should also be able to receive SIBs transmitted by the network reliably. Without reading system information, a UE cannot attempt to establish a radio resource control (RRC) connection with the network.
In LTE networks, system information blocks, such as SIB1, SIB2 and other System Information (SI) messages comprise network-access related information for incoming UEs. These system information blocks are scheduled in the physical downlink shared channel (PDSCH), and their location is indicated by physical downlink control channel (PDCCH). The cyclic redundancy check (CRC) of PDCCH is scrambled by the SI radio network temporary network identifier (SI-RNTI) as an indication of broadcast or multicast message.
In future releases of 3GPP LTE, UEs with special capabilities may be required to be supported by the LTE network. For example, Category 0 UEs may require special support from the network. In some circumstances, these UEs may be low power devices with no or limited user interaction, so called machine type communication (MTC) terminals. These UEs may comprise only one physical antenna and therefore have limited coverage. Further the UE capability may be limited to half-duplex to conserve the power. When such a UE enters a LTE network, the primary job for the UE is to find whether the network is capable of supporting functionality of such UEs. To support these types of UEs, a network should be able to provide good coverage, because reception capabilities of these UEs are very limited.
One way of enhancing the coverage of the SIBs is by increasing the transmit power of radio resources assigned for the PDSCH carrying the SIBs and the associate PDCCH. However, there are various disadvantages with this approach. Due to limits on the total transmit power, increasing the power of these resources may negatively impact network spectral efficiency because of transmit power limitation o on the resources used for the regular UEs (i.e. non-special UEs). Moreover, even if transmit power is increased for the PDSCH and PDCCH carrying the SIBs, there is no guarantee that the performance gain is improved. When all the surrounding cells also increase the transmit power levels on the same radio resources, the signal to interference levels are not improved.